test SetFeaturedPost use case

backend/tests/Unit/Post/UseCases/SetFeaturedPostTest.php

@@ -0,0 +1,171 @@
+<?php
+
+namespace Tests\Unit\Post\UseCases;
+
+use App\Exceptions\BadRequestException;
+use App\Exceptions\ForbiddenException;
+use App\Post\CreatePostDto;
+use App\Post\Post;
+use App\Post\UseCases\SetFeaturedPost\SetFeaturedPost;
+use App\Post\UseCases\SetFeaturedPost\SetFeaturedPostRequest;
+use DateTimeImmutable;
+use DateTimeZone;
+use DomainException;
+use Tests\Fakes\FakePostRepository;
+use Tests\TestCase;
+
+class SetFeaturedPostTest extends TestCase
+{
+    private FakePostRepository $postRepo;
+
+    private SetFeaturedPost $useCase;
+
+    private DateTimeImmutable $now;
+
+    protected function setUp(): void
+    {
+        $this->now = new DateTimeImmutable(
+            '2026-05-06T12:00:00',
+            new DateTimeZone('UTC'),
+        );
+        $this->postRepo = new FakePostRepository;
+        $this->useCase = new SetFeaturedPost($this->postRepo);
+    }
+
+    private function seedPost(): Post
+    {
+        return $this->postRepo->create(new CreatePostDto(
+            userId: 1,
+            title: 'A',
+            body: 'B',
+            createdAt: $this->now,
+        ));
+    }
+
+    public function test_non_admin_throws_forbidden(): void
+    {
+        $post = $this->seedPost();
+        $this->expectException(ForbiddenException::class);
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $post->getId(),
+            slot: 1,
+            requesterIsAdmin: false,
+        ));
+    }
+
+    public function test_invalid_slot_throws_bad_request(): void
+    {
+        $post = $this->seedPost();
+        $this->expectException(BadRequestException::class);
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $post->getId(),
+            slot: 3,
+            requesterIsAdmin: true,
+        ));
+    }
+
+    public function test_zero_post_id_throws_bad_request(): void
+    {
+        $this->expectException(BadRequestException::class);
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: 0,
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+    }
+
+    public function test_unknown_post_throws_domain_exception(): void
+    {
+        $this->expectException(DomainException::class);
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: 999,
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+    }
+
+    public function test_admin_assigns_slot(): void
+    {
+        $post = $this->seedPost();
+
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $post->getId(),
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+
+        $reloaded = $this->postRepo->find($post->getId());
+        $this->assertSame(1, $reloaded->getFeatureSlot());
+    }
+
+    public function test_assigning_same_slot_evicts_previous_post(): void
+    {
+        $first = $this->seedPost();
+        $second = $this->seedPost();
+
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $first->getId(),
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $second->getId(),
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+
+        $this->assertNull(
+            $this->postRepo->find($first->getId())->getFeatureSlot(),
+        );
+        $this->assertSame(
+            1,
+            $this->postRepo->find($second->getId())->getFeatureSlot(),
+        );
+    }
+
+    public function test_two_posts_can_occupy_separate_slots(): void
+    {
+        $first = $this->seedPost();
+        $second = $this->seedPost();
+
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $first->getId(),
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $second->getId(),
+            slot: 2,
+            requesterIsAdmin: true,
+        ));
+
+        $featured = $this->postRepo->findFeatured();
+        $this->assertCount(2, $featured);
+        $this->assertSame(1, $featured[0]->getFeatureSlot());
+        $this->assertSame(2, $featured[1]->getFeatureSlot());
+    }
+
+    public function test_moving_post_to_other_slot_clears_old_slot(): void
+    {
+        $post = $this->seedPost();
+
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $post->getId(),
+            slot: 1,
+            requesterIsAdmin: true,
+        ));
+        $this->useCase->execute(new SetFeaturedPostRequest(
+            postId: $post->getId(),
+            slot: 2,
+            requesterIsAdmin: true,
+        ));
+
+        $this->assertNull(
+            $this->postRepo->findByFeatureSlot(1),
+        );
+        $this->assertSame(
+            $post->getId(),
+            $this->postRepo->findByFeatureSlot(2)->getId(),
+        );
+    }
+}